JPH04193552A - Image recorder - Google Patents

Abstract

PURPOSE:To print an image in a high quality and to print the widths of lines equally by reading pixels of conductive data and data of a plurality of adjacent pixels thereto from a memory at the time of forming the data of the pixels, and deciding whether print information has vertical lines or not. CONSTITUTION:For example, when conductive data of pixel D5 is formed, total 9 pieces of a pixel D5 as a center, two adjacent pixels D4, D6 of the same row as the pixel D5 and the same fist pixels D1-D3, D7-D9 of front and rear rows are read. One of these data read from a memory is supplied directly to a selector 6, and one is supplied to the selector 6 through a vertical line detector 4. A print controller 5 generates twice a control signal per one print of one row, and the selector 6 is alternately switched like data to be input to the selector 6 directly at the time of printing first time (first/second rows), and data to be input to the selector 6 through the vertical line detector at the time of printing second (second/second rows).

Description

[Detailed description of the invention] [Industrial application field] The present invention uses a thermal head to generate two characters.

The present invention relates to an image forming apparatus that prints an image on recording paper based on an input signal such as an image (hereinafter referred to as an image input signal), and particularly to an image forming method suitable for improving the quality of the printed image. [Prior art] Image recording methods using thermal heads include thermal recording methods in which thermal energy is applied to thermal paper containing an image forming material such as leuco paint to develop color, and heat-melting ink or sublimation. A thermal transfer recording method is known in which thermal energy is applied to an ink paper coated with a polyester paint ink on a base film made of polyester, etc., in close contact with the recording paper, and the ink is transferred onto the recording paper to develop color. Among these, the thermal transfer method, which uses sublimation paint ink, can perform density gradation recording from 64 to 256 gradations by controlling the energization time to the thermal head heating element, so it is suitable for video printers. It is becoming the mainstream printing method for full-color image recording devices such as .

On the other hand, image creation and processing using computers.

With the development of editing technology, straight lines and curved lines, such as ruled lines.

There is an increasing demand for printing text and images together with images.

The video printer described above uses a thermal line head in which several hundred or more rectangular heating elements are formed in rows, and the ink paper and recording paper are moved in a direction perpendicular to the rows of heating elements, one row at a time. One printed image is obtained by repeatedly printing each pixel data. In order to obtain high-quality image prints with a video printer,
It is necessary that the colored dots are connected smoothly without gaps, and for this reason, the length of the heating element of the thermal head in the paper feeding direction (hereinafter simply referred to as length) must be considerably longer than the feeding pitch of one line. It is usually chosen to be the second (1.5 to 2 times).

However, when printing vertical lines or horizontal lines such as ruled lines using a thermal head with such a heat generating element shape, as shown in Fig. The line width W is one line in the paper feed direction (hereinafter referred to as ``W'').

A problem has arisen in that the line #iW2 (referred to as a horizontal line) is 1.5 to 2 times thicker than the line #iW2. This is due to the following reasons. (1) When the vertical lines in FIG. 5 are printed, adjacent heating elements generate heat at the same time, so the temperature of one heating element increases due to mutual thermal interference between adjacent elements. On the other hand, when printing horizontal lines, the adjacent heating elements are not generating heat, so they are in an independent heating state, and the heating temperature of the heating elements corresponding to the horizontal lines is lower than when printing vertical lines. This situation is shown in FIG. The heat generating element has a temperature distribution where the temperature is high in the center and low at the edges, and ink transfer occurs in the area where the temperature reaches a certain level and color develops, so the line width of vertical lines is better than that of horizontal lines. It becomes thicker than the line width. (2) Since printing is performed line by line while moving the recording paper at a constant speed, the relative moving distance between the heating element and the recording paper changes depending on the time the heating element of the thermal head is energized, and the length of one colored dot changes. . When printing images, pH 61h Soot 1. Since the length of the first track element is designed, at high concentrations where one energization time is long, the length of the colored dots becomes longer than the feed pitch of one line.

Normally, characters and ruled lines are often printed with high-density data, so the printing width of vertical lines tends to increase. On the other hand, since the printed width of the horizontal line does not expand beyond the width of the heating element, the printed line width of the vertical line is thicker than the printed line width of the horizontal line.

As a way to eliminate uneven print widths of vertical and horizontal lines,
It is conceivable to shorten the length of the heating element of the thermal head, but for the reasons mentioned above, in order to make the printed line width approximately equal, it is necessary to make the length of the heating element much shorter than before. As a result, when printing regular images, the length of colored dots becomes noticeably shorter in low-density areas, resulting in gaps between dots that appear as white streaks, and the effects of unevenness on the surface of the recording paper. This had the disadvantage that it was more susceptible to damage, resulting in grainy prints.

[Problem to be solved by the invention]

As mentioned above, in conventional image recording devices, it is difficult to achieve both the goals of achieving high image quality by producing smooth colors when printing images, and the goal of making the line widths equal when printing vertical and horizontal lines. It was difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image recording apparatus that can print one image with high quality when vertical lines and horizontal lines are printed together with an image, and can also print lines with equal width.

[Means to solve the problem]

In order to achieve the above object, the image recording device of the present invention includes:
(1) Print one line twice at equal intervals. (2
) “When creating energization data for each pixel, that pixel is a “vertical line”.
A means of detecting whether or not it corresponds to a part of the vertical line J is provided.
The 1st/2nd line is printed with the original data only when it is determined that the data is part of the
), the printed line width is reduced. As a means of achieving this, after the image memory temporarily stores data representing the recording density of each pixel, when creating the energization data for each pixel, the data of that pixel and the data of a plurality of pixels adjacent to that pixel are read out, so that the pixel is It is determined whether the pixel is part of a line, that is, a straight line in the direction parallel to the row of heating elements, and if it is determined that it is not a vertical line, the input data is output as is, but only if it is determined to be a vertical line, the pixel is A vertical line detection circuit is provided that replaces the value with a small theta. By means of the switching means, when printing the 1st/2nd line, the data from the image memory is input as is to the energization data creation means of the thermal head, but when printing the 2nd/2nd line, data is input from the image memory through the vertical line detection circuit mentioned above. Output to energization data creation means. As a result, the energization data on the 2/2 line becomes small only when vertical lines are printed, and the same energization data as on the 1/2 line is otherwise sent to the thermal head.

[Effect]

When creating energization data for each pixel, the vertical line detection circuit reads data for that pixel and a plurality of pixels adjacent thereto from the image memory, and determines whether print information is a vertical line. For example, if the pixel of interest is the Nth pixel in the M row in the image frame memory, the Nth pixel in the M-1, M+1 rows and the N-1, N+1 pixel in the M row are It is then read to determine whether the pixel of interest corresponds to part of the vertical line. For normal image input that does not correspond to vertical lines, the vertical line detection circuit outputs the input pixel data as is to the thermal head energization data creation means.

As a result, each line is printed twice with the same energization data, making it possible to obtain high-quality image prints that are smoothly continuous in the paper feeding direction. On the other hand, when a vertical line such as a ruled line is input, the data on the 1/2nd line is printed as is, but the energization data on the 2/2nd line is set to O, for example. As a result, the print line width becomes 1/2 line. Normally, ruled lines are often printed with high density (large input data), so the printed line width of a vertical line of 1/2 line is almost the same as the printed line width of a horizontal line (in an isolated state of heat generation). The energization data on the 2/2nd line does not need to be set to O, and the same visual effect can be obtained by setting it to appropriately small data.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a block diagram showing an example of a signal processing circuit configuration of an image recording apparatus according to the present invention.

In FIG. 1, 1 is a memory for temporarily storing digitized input image data (including characters, lines, etc.), 2 is an image data writing control means for controlling writing to the memory 1, and 3 is a memory for temporarily storing digitized input image data (including characters, lines, etc.); An image data readout control means 4 for controlling readout determines whether a pixel for which a plurality of data is to be created from a plurality of data read from the memory 1 is part of a vertical line, and determines that the pixel is a vertical line. 5 is a print control circuit that generates a control signal for each print line; 6 is a print control circuit that generates small data (including 0) only when the line to be printed is 1
/Selector that switches the output depending on the 2nd line or 2/2nd line, 7
The energization data creating means 8 which creates energization data for the thermal head from the output from the selector 6 is a thermal head in which heating elements are arranged in a row. Although not shown in FIG. 1, the thermal head 8 is pressed via ink paper against recording paper wound on a platen rotating at a constant speed, and prints one line at a time sequentially as the platen rotates. It is.

The printing operation of the present invention will be explained below with reference to FIG.

A portion of the input digital image data is stored in the memory 1 by a control signal from the image data writing control means 2. The memory 1 is, for example, a frame memory that stores one screen (1 frame) of a display, or a plurality of line memories that stores multiple lines of data. When printing starts, ink paper and photographic paper are first set on a platen (not shown), and when the thermal head 8 detects that it has come to the top position of printing on the photographic paper, a print start signal is issued.
The image data stored in the memory 1 is sequentially read out, and a drive signal for the thermal head 8 is created by the energization data creation means 7.

Here, according to the control signal of the image data readout control means 3, the data is read from the memory 1 as shown in FIG. 2, for example.
Three nine pixel data are read out. That is, for example, when creating energization data for pixel 1, one pixel D5 is the center, and two adjacent pixels D4 . D...
and the same pixel D~D in the previous and subsequent rows, D7~
D, a total of nine items are read out. One of these data read from the memory is directly supplied to the selector 6, and the other is supplied to the selector 6 via the vertical line detection circuit 4. The print control circuit 5 outputs 2 bits per line of printing.
The data is directly input to the selector 6 during the first printing (line 1/2), and the data is input manually to the selector 6 during the second printing (line 1/2).
When printing (line 72), the selector 6 is alternately switched such that the data is input to the selector 6 via the vertical line detection circuit. As a result, if the pixel D5 does not correspond to part of the vertical line, the same data is sent to the energization data creation means 7 for both printings of one line, and only if it corresponds to part of the vertical line, the same data is sent to the energization data creation means When printing the eyes, small data replaced by the vertical line detection circuit is sent to the energization data creation means 7. The energization data creation means 7 receives data from the selector 6 and outputs the data from the print control circuit 5.
In accordance with the control signals, data for energizing the thermal head heating elements corresponding to the pixel of interest is sequentially created. For example, data of the nine pixel data D□ to D9 to D5 is sampled, and a current application time corresponding to the data is generated. If the pixel D5 falls within the vertical line, the data of the pixel D5 that has passed through the vertical line detection circuit is small when printing the 2nd/2nd line, so the energizing time of the corresponding heating element is shortened. , the color density becomes lower and the length of one pixel becomes visually shorter.

An example of a method for determining whether a line corresponds to a vertical line in the vertical line detection circuit 4 shown in FIG. 1 will be described below. [DMN
] is the Nth pixel data in the Mth row. When printing ruled lines or characters, the ruled lines themselves are often printed with large data at or near the highest density, and are often significantly different from the color and density of the background in terms of data.

Therefore, pixel data [DMIN-1, [DM.

, , and should be large data approximately equal to [DIJ, N], and adjacent pixel data in the preceding and succeeding rows (M-1 rows and 5M+1 rows) should be data that is significantly different. In this way, by comparing a total of nine adjacent pixel data centered on [)MN], it is possible to determine whether or not [0M11] corresponds to a vertical line. Note that various criteria can be set for the method 9 for determining whether a line is a vertical line, and the number of adjacent pixels used for determination is not limited to this example.

When the pixel [DIJN] is determined to be part of a vertical line by the method described above, the vertical line detection circuit 4 changes the data of the pixel [DIJN] to small data. Reading pixel data,
The replacement may be performed by a microcomputer.

FIG. 3 is a diagram showing an example of the shape of the heating element of the thermal spatula 1- of the image recording apparatus of the present invention, and FIG. 4 is a schematic diagram showing an example of the shape of colored dots when printed with the thermal head shown in FIG. 3. It is.

In FIG. 3, 9.10.11 represents three of the heating elements of the thermal head formed in a row; 12.
13 and 14 are electrodes for supplying current to each heating element. WH is l1li of the heating element (length in the element row direction)
, L8 represents the length of the heating element (length in the paper feeding direction). In addition, 15 is an insulating part between heating elements, and usually 10~
It is 20 μm. The length of the colored dot (in the paper feed direction) is considerably shorter than the length Ll of the heating element in low-density printing where the heating time is short.For this reason, one line is
With conventional image recording devices, which print in multiple steps, in order to connect colored dots smoothly without any gaps, it is necessary to
<I had to choose L8. Since the image recording apparatus of the present invention prints one line by dividing it into two parts, the shape of the heating element is W. ”=LH or W□>LH is selected.

In Fig. 4, (A) shows the colored dot shape when one horizontal line (one dot) is printed, and (B) shows one (one dot) horizontal line.
An example of the colored dot shape when a vertical line (1 line) is printed is shown. When printing horizontal lines, the adjacent heating elements are not generating heat, so one colored dot 'l' shown as 16°17,... ! W p 1 and length LPI are small, and the printed horizontal line width is represented by W, .

On the other hand, when printing vertical lines, the width of the colored dots is wider than when printing horizontal lines because the adjacent heating elements generate heat at a high temperature.
Length and width, 18.19. The width of one colored dot indicated by ... is Wl (>W21), and the length is L2□ (>LP,
). FIG. 4 shows a case where the energization data on the 2/2nd line is O when printing vertical lines, and the printed vertical line width is LP2. As a result, the horizontal line print width W
P, and the vertical line print @L,2 are almost equal. Note that when the data on the 2/2nd line is small, the coloring density is low, so visually the same effect can be obtained.

When printing a normal image input that does not include vertical lines or horizontal lines, the 2/2nd line is printed with the same data as the 1/2nd line, so for example, 16 and 17 in Fig. 4 are printed as 1. form a pixel. Therefore, the density distribution of the colored dots in the paper feeding direction can be flattened, and the colored dots can be smoothly connected, so that high-quality prints without roughness can be obtained.

The components of the present invention include vertical line pressure detection, providing an arithmetic circuit between the memory and the energization data creation means, printing one row by dividing it into two parts, and printing in the direction parallel to the row of heating elements. Only when printing lines, the energization data on the 2nd/2nd line should be made small (including O), and if the same effect can be obtained, the signal processing circuit configuration can be implemented as shown in Figure 1. β is not added to the example.

Furthermore, although the above explanation has been made using a thermal transfer recording method using a sublimable dye as a representative example, the present invention is also applicable to other methods, that is, a thermal recording method using thermal paper, or a thermal transfer recording method using heat-melting ink. It is possible.

[Effects of the Invention] According to the present invention, one row is divided into two parts and printed, and the pixels to be printed are vertical lines, that is, straight lines in only one row in the direction parallel to the row of thermal head heating elements. Determine whether or not.

Only when it is determined to be a vertical line, the 1/2nd line is printed with the original data, but the 2/2nd line is printed with a straight line in the direction parallel to the heating element row (
The printing line widths of a vertical line (vertical line) and a straight line (horizontal line) in a perpendicular direction can be made almost equal. In addition, for normal image input that does not correspond to vertical lines, one line is printed twice with the same data, so the density distribution of colored dots in the paper feed direction can be flattened, and colored dots can be printed twice. This allows the images to be connected smoothly, making it possible to obtain high-quality prints without any roughness.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a signal processing circuit of an image recording apparatus of the present invention;
FIG. 2 is a diagram showing an example of a signal processing method in the signal processing circuit shown in FIG. Figure 3 is a diagram showing the shape of colored dots produced by the thermal head described in Figure 3, Figure 5 is a diagram showing the shape of colored dots produced by the thermal head of a conventional image recording device, and Figure 6 is the diagram showing the heat generated by the heating element of the thermal head. It is a temperature explanatory diagram. memory,

Claims (1)

[Claims] 1. Using a thermal head in which heating elements that can selectively generate heat according to energization data are arranged in a row, the recording paper is moved in a direction perpendicular to the row of heating elements, one row at a time. In an image recording device that obtains a predetermined printed image by repeatedly printing pixels, there is an image memory that temporarily stores data representing the recording density of each pixel, and when creating energization data for each pixel, data for that pixel and A detection circuit is provided that reads data of a plurality of pixels adjacent to the pixel and determines whether the pixel is part of a line (referred to as a "vertical line") in a direction parallel to the row of heating elements. If it does not correspond to a part of the "vertical line", the heating element corresponding to that pixel is made to generate heat twice in each 1/2 line using the same energization data to print one line, and the above detection circuit detects the "vertical line". For pixels that are determined to be part of the pixel, the 1st/2nd row will be printed with energization data that corresponds to the density data of that pixel, but the 2nd/2nd row will be printed with small energization data (including 0). An image recording device characterized by: 2. The output from the image memory is branched into two, one is directly input to the switching means, the other is input to the switching means via the detection circuit, and the output from the switching means is input to the thermal 2. The image recording apparatus according to claim 1, wherein the energization data is input to the head energization data generating means, and is switched between when printing the 1/2 line and when printing the 2/2 line. . 3. The shape of the heating element of the thermal head is such that its width (element dimension in the heating element row direction) is approximately equal to its length (element dimension in the paper feeding direction), or the width is larger than the length. The image recording apparatus according to claim 1, characterized in that: